Sixties folk-rock pioneers the Byrds are one of the best-known bands in rock history, while '80s folk-rock refiners the Go-Betweens never really made it much past cult status, even in their native Australia or in England, where they were based for much of their career. Yet, each band in its own way has been underappreciated. And, with the release of retrospectives of their work, both bands are due to be rediscovered.

The Byrds: 'The Byrds' The matter-of-factly titled "The Byrds" (Columbia/Legacy) is a 90-song, four-disc or cassette package that functions as a greatest hits album, a rarities collection and a comeback. All those roles can be questioned -- the four albums the band made during 1966-68, at least, deserve to be heard in their entirety, many of the rarities have already appeared on a package called "Never Before" and the six songs newly recorded in 1990 are not equal to the classic material -- but this stratospheric music quickly drowns out any questions.

Save for the occasional substandard collector's item (mostly David Crosby songs such as "Psychodrama City" or "Triad," which richly deserved their outtake status), the first two discs of this collection are simply gorgeous. The styles being invented -- folk rock, of course, but also the raga-rock of electrifying "Why" and the country rock of "Old John Robertson" and the "Sweetheart of the Rodeo" album -- underpin all non-metal guitar rock that was to follow. These two discs could reasonably be issued as "The Roots of '80s College-Radio Rock." Featured are "Mr. Tambourine Man," "Turn! Turn! Turn!," "The Bells of Rhymney" and "My Back Pages," all among the band's most successful borrowings from the Bob Dylan and Pete Seeger songbooks.

Yet many of the Byrds' most successful songs were originals, written by Gene Clark, who dominated the songwriting until he quit during the recording of "5D," the third album, or later by Roger McGuinn, Chris Hillman and Crosby. They include such hits as "So You Want To Be a Rock 'n' Roll Star" and the brilliant "Eight Miles High" -- one of the first singles to be banned for drug references, though McGuinn insisted it was about flying to London. And they include such relative obscurities as "She Don't Care About Time" (presented here in a never-released version in which a harmonica duels with McGuinn's Bach-rock solo) and "She Has a Way," a great Clark song that was cut from the band's first album.

Such previously unreleased tracks as the Byrds' version of Jackson Browne's "Mae Jean Goes to Hollywood" are mere curiosities, but there is one group of rarities here that is more than footnote material: "The Byrds" features several outtakes from "Sweetheart of the Rodeo," the album that marked the beginning and end of Gram Parsons's tenure as a Byrd. Not only is the country-rock innovator, whose short career ended with his mysterious 1973 death, heard on such rejects as "Reputation" and "Lazy Days" (later recorded by Parsons's Flying Burrito Brothers), he also sings "I Am a Pilgrim," "You Don't Miss Your Water" and "One Hundred Years From Now," vocals that were replaced by McGuinn's on the versions ultimately issued. No Parsons fan should miss these.

Even the Byrds of 1969's "Dr. Byrd and Mr. Hyde," depleted by defections that left McGuinn the only surviving original member, had exceptional power; that album's version of Dylan's "This Wheel's on Fire" is hard-edged noise-pop that My Bloody Valentine fans will find quite contemporary.

After that, though, the third and fourth discs begin to plod. The best of such later albums as "Ballad of Easy Rider" and "Untitled" is respectable but uninspired -- much like the new material McGuinn, Hillman and Crosby recorded last August to bring the project full-circle. It's good that these trailblazers are still active -- McGuinn's first solo album in years is scheduled soon, Hillman has the Desert Rose Band and Crosby, the most successful and most notorious ex-Byrd, has apparently conquered a longstanding drug problem -- but there's nothing in such new songs as "Love That Never Dies" to suggest they will ever again attain the level of "Eight Miles High."

The Go-Betweens: '1978-1990' The Byrds were never a very personal band -- the wide selection of songwriters, both from outside and within, guaranteed that. The band's fundamental message was simply its sound, a soaring, luminous whoosh of carillon-like 12-string and high harmonies. By contrast, the Go-Betweens were hardly musical innovators, but Robert Forster and Grant McLennan, the band's founding duo, were among the '80s' finest pop songwriters, charting "my feelings in the bedroom, Brisbane, driving my car and anything from overheard conversations" -- as Forster puts it -- with elegant melodies and poetic (but never purple) lyrics.

The Go-Betweens never recorded a cover, and released only one song that gave songwriting credit to any other members of the band, which gradually grew to a quintet before splitting early this year. Though the band progressed from the terse, punky sound of the earliest recordings through the sophisticated chamber-rock of the "Spring Hill Fair" and "Tallulah" albums to the almost-sweet acoustic pop of its final album, "16 Lovers Lane," there was never any possibility of the band being swallowed up by the machinery. Forster and McLennan's vision was always paramount.

The 28-song, two-pocket vinyl version of "1978-1990" (Beggar's Banquet/RCA) makes that especially clear. The first disc follows the band's development chronologically, while the second gives one side to Forster and the other to McLennan for quirkier, more personal summations of each's work, featuring three songs that have never been released before.

For space reasons, the CD cuts six songs, including one of the never-befores and several others, from long-deleted singles, that only a dedicated scholar will ever turn up on his own. Still, even the CD contains enough classic songs -- including the evocative "Cattle and Cane," the exquisite "Bachelor Kisses," the bitter "Draining the Pool for You" and the jumpy "I Need Two Heads" -- to qualify as essential to connoisseurs of the guitar and the human voice.

The Go-Betweens' first single, "Karen," was a paean to a librarian, and this album confirms their literariness. Each song is the subject of a brief note by its author, and some are poems in their own right. Even those who have a complete Go-Betweens collection will want these smart, funny notes, not to mention "The Sound of Rain" (not on the CD), "You Won't Find It Again" and "Second-Hand Furniture," in which a divorced man happens upon the inanimate members of his former household in a store window.

Moving, haunting but unsentimental, "Furniture" is both a great addition to the band's canon and an encapsulation of its virtues. Forster's excellent solo debut, "Danger in the Past," has been released in England and is due stateside early next year. A McLennan album has been recorded, and should follow soon after.